If it happens again in the final round of the HP Byron Nelson Championship, it could cost him the tournament.

Bradley enters Sunday at 13 under and with a one-shot lead over Sang-Moon Bae. He's primed to win his second HP Byron Nelson and the fourth PGA TOUR event of his young career. This tournament, with its hot, humid conditions, 15-20 mph winds and a challenging course that has gotten tougher throughout the week, calls for a grinder's mentality, and Bradley seems to be a perfect fit.

But he must figure out the 18th. The 429-yard, par-4 dogleg left closing hole at TPC Four Seasons Resort has become the only thing Bradley hasn't conquered in an otherwise stellar performance.

Bradley shot a course-record 10-under 60 on Thursday, but bogeyed the 18th (his ninth hole in the first round) after bailing out to the right off the tee. He shot a 1-under 69 on Friday -- a round that satisfied him more than the 60 -- but bogeyed the 18th after another bailout drive.

On Saturday, in a round of 68 that he would later describe as one of his most solid of the year, he was leading by two shots when he reached the 18th hole, which has ranked this week as the third toughest on the course. He opted for a more aggressive line, closer to the water guarding the left side of the fairway. His ball stayed dry -- barely -- but landed behind a boulder, forcing Bradley to chip back into the fairway and resulting in a bogey when his par putt from off the green just slid by the hole.

"Tomorrow I'm going to stripe it," Bradley said. "I'm due. I know that I'll hit a good one tomorrow."

Just like the state in which it resides, the 18th is not a hole you want to mess with. And to be fair, Bradley is not the only player who finds it troubling.

In 2010, Jason Day found the water at 18 three times, but survived to win his first PGA TOUR event by two strokes. Of course, it helped that his playing partner on the final round, Blake Adams, also found the water that day.

Three years later, Day still hasn't forgotten how the 18th treated him. Asked about it earlier this week, his first reaction was simply, "Blow it up."

But he did call it a "good, tough finishing hole. If you have the lead, it makes you think twice about what kind of shot you want to hit."

On Saturday, one of Bradley's playing partners, Tom Gillis, birdied the 18th when he holed out from the greenside bunker. That two-shot swing allowed Gillis to move within two of the lead going into Sunday.

Gillis said he didn't like the hole when he saw it on his first visit to the HP Byron Nelson 10 years ago. He didn't have a good strategy on it, didn't feel comfortable on it.

"I just thought it was hard," Gillis said. "Just incredibly hard."

And now?

"The more I play it, the more I'm starting to like it," Gillis said.

When Bradley won this event two years ago, he parred the hole in three of the four rounds. Then in the playoff with Ryan Palmer, Bradley won with a par at the 18th after Palmer hit his second shot in the water.

After providing Bradley with such good fortune that year, perhaps the 18th is seeking payment this week.

Unlike the first two rounds, Bradley actually liked his tee shot at the hole on Saturday. He "smashed" it ... but as it drifted to the left, he feared he might find the water.

"Just didn't take the wind," he said. "It's a tough hole for everybody, a lot of bogeys on that hole."

Three of those bogeys belong to Bradley. For the other 17 holes this week, he's a collective 16 under with one eagle, 19 birdies and 5 bogeys. In fact, the only hole he has bogeyed on the back nine all week is the 18th.

His struggles on the 18th have kept the rest of the field close to the lead, and has given them hope that Sunday will not be an 18-hole coronation.

"He's a world-class player and he's playing good," said Scott Piercy, who'll start in fourth place, three shots off the lead. "He will probably continue to play good." But, added, Piercy, "This golf course had a lot of bogeys on it."

Bae, the second-year player from South Korea looking for his first TOUR win, said he will focus only on his own game, and not get caught hoping Bradley makes mistakes. But, he warned, "Nobody knows. Wind will blow."

Bradley doesn't mind. He likes the tough conditions. He welcomes it. He's won a PGA Championship and a World Golf Championship event (the Bridgestone Invitational) to go with his Byron Nelson win. Those things don't come cheap.

"When it's tough conditions," he said, "I think that the players that are ready for it play well."

Nobody has played better this week on the first 17 holes at TPC Four Seasons than Bradley. But if this tournament and his fate comes down to the 18th hole on Sunday, you better hold on tight. It could be a wild ride.